The present invention relates generally to mechanical devices used in surgical procedures to occlude a vessel or duct, and more particularly, to an instrument that can apply a pre-formed, spring-loaded clip used during surgery to clamp around a vessel or duct, such as cystic duct or cystic artery, and thereby obtain homeostasis or occlusion.
Those skilled in the art will appreciate that the use of clips for homeostasis or ligation during surgical procedures is well known. U.S. Pat. Nos. 4,976,722 and 4,979,950 for example, described prior art clips that are formed of titanium wire. Prior to use, these clips are “U-shaped” with a rectangular cross-section. Application of these prior art clips is normally effected by means of a crushing action produced by a clip applier, such as that disclosed in U.S. Pat. No. 5,030,226. Such crushing action permanently deforms the clips, making them difficult to remove or re-position. Another problem with crush clips is that vessels and tissue often shrink after occlusion owing to the onset of necrosis, for example. Because these type clips have no means for compensating for shrinking tissue, they lose their occlusion properties.
Numerous spring clips have been developed for occluding tissue. U.S. Pat. Nos. 4,966,603, 4,274,415, 5,833,700 and 6,350,269 disclose examples of spring clips. One problem with the clips described in the '603, '415, and '700 patents is that the occlusion force exerted by the clips approaches zero as the opposing occlusion members come into contact. Thus, for very thin tissue, the clips supply nearly zero occlusion force.
Other problems are presented by the clip of the '269 patent. For example the clip of the '269 patent is too wide for many intricate procedures and its configuration is difficult to manufacture. In addition, this clip is difficult to remove under laparoscopic conditions.
Some spring clips, such as those clip described in U.S. Pat. No. 4,556,060, are designed for placement on tissue in the surgical field by hand. Other clips, such as that described in U.S. Pat. No. 4,274,415, are applied using applicators that are suitable for use in open surgery but not for laparoscopic surgery. One applicator that is suitable for use in laparoscopic surgery is the applicator disclosed in the '269 patent. The clip and applicator combination of the '269 patent have several problems, however. For example, the clip has a narrow proximal end and the feed track in the clip holder is relatively wide. This causes the clip stack to kink, which causes excessive friction during clip feed. This can result in the clip pusher slipping over clips and clips jamming. Also, the jaws of the applicator are necessarily wide in order to accommodate the wide distal end of the clip. This does not allow adjacent clips to be placed in close proximity as is often required in delicate procedures. Another disadvantage of the '269 system is that surgeons are accustomed to viewing clips as they are being applied. Crush clips, for example, are fully visible before crushing. Viewing of the clip during application in '269 is limited to the view of a small portion of the clip through one of two small windows in the jaws. Yet another problem is that the applicator described in '269 patent uses a sacrificial clip to push the last usable clip onto the jaws for application. The sacrificial clip remains in the applicator, unusable, since there is no reliable means to push it out. Sometimes, the pusher clip is partially fed into the jaws, which causes the jaws to become attached to the tissue with no way to extricate the clip and free the jaws. Finally, resetting the applicator to the initial state so that the applicator is ready to place a second clip is often a problem.
What is needed is a simple-to-manufacture, easy-to-remove, narrow spring clip that maintains a substantial occlusion force to the occlusion members of the clip when they are at or near the closed position so that small vessels and ducts can be adequately occluded.